1. Field of the Invention
This invention relates to a structure of a floor slab bridge in a bridge built up in a river or on land, and more particularly to a structure of a floor slab bridge in which a columnar H-shaped steel is used as a main girder material.
2. Related Art
A floor slab bridge is disclosed by Japanese Patent Application Laid-Open Publication No. H09-221717 as typically illustrated in its FIGS. 1 and 2, in which steel sheet piles 11 are used as a bottom plate, T-shaped steels or H-shaped steels (main girder member 13) are welded to the steel sheet piles 11 such that the T-shaped steels or H-shaped steels are spacedly arranged thereon. Adjacent steel sheet piles 11 are joined by pawls 12 disposed at left and right side end faces of each steel sheet pile 11. Concrete is placed in a space between an upper flange of each T-shaped steel or H-shaped steel and the steel sheet pile 11 through a concrete inlet port which is formed between the upper flanges of each T-shaped steel or H-shaped steel so that a lower concrete layer is formed, and concrete is placed on the upper flange so that an upper concrete layer is formed, wherein the upper concrete layer is to be joined with the lower concrete layer through the concrete inlet port.
Similarly, FIG. 5 of the above publication shows a floor slab bridge in which a plurality of T-shaped steels or H-shaped steels are arranged in side-by-side relation on a bottom plate 3 composed of a single steel plate and concrete is placed thereon.
In those floor slab bridges, a side plate 16 is applied to the outer side surface of the side concrete layer placed on the outer side surface of the leftmost or rightmost T-shaped steel or H-shaped steel, and in the floor slab bridge shown in FIGS. 1 and 2, a PC steel material 18 is pierced through a web plate formed of T-shaped steel or H-shaped steel, which are arranged in a side-by-side relation, a lower concrete layer and a block which is called a cross girder 19, from the outer side surface of the side plate 16. Both ends of the PC steel material 18 are fastened at the outer side surfaces of the side plates 16, and play at the joint part of the pawl 12 is set to a maximum, thereby applying a pre-stress to the concrete layer. Necessarily, the PC steel material 18 used as this pre-stress means is left in its exposed state at the fastening parts on both ends at the outer side surfaces of the side plates 16.
In the above-mentioned conventional structure(s), the bottom plate is formed by the steel sheet piles 11, and the T-shaped steels or H-shaped steels are spacedly arranged in side-by-side relation on the bottom plate as in the manner mentioned above. Play at the joint part of the pawl 12 of the steel sheet pile 11 is set to a maximum. After the concrete is cured, the PC steel material 18 is fastened at the outer side surfaces of the side plates 16, thereby applying a pre-stress to the concrete layer. The PC steel material 18 pierces through the cross girder 19, with play, thus enabling a fastening which can apply the pre-stress. Accordingly, the PC steel material 18 is not joined with the concrete at all. This means that the PC steel material 18 does not function as a concrete reinforcement.
Therefore, if a vertical load (live load) attributable to a passage of vehicles, etc. is applied to the floor slab bridge, a shearing force would act on the concrete layer which would induce cracking of the concrete layer.
Moreover, since the PC steel material 18 is fastened at the outer side surfaces of the two side plates 16, the load is totally applied to the fastening parts of the side plates 16, thus resulting in a collapsing and/or twisting of the side plates 16.
In addition, since the fastening parts are exposed from the side plates 16, i.e., from the concrete layer, the fastening parts become rotten due to wind, rain or the like so as to degrade their original function and to spoil the outer appearance of the floor slab bridge.
Moreover, it is very troublesome to fillet weld each and every T-shaped steel or H-shaped steel over its entire length to the bottom plate 3 and the steel sheet piles 11 at constant intervals. Thus, the labor time is increased and the cost is increased, too.
The present invention has been accomplished in view of the above problems.
It is, therefore, an object of the present invention to provide a structure of a floor slab bridge which can be properly formed by forming a main girder structure using commercially available columnar H-shaped steels and applying concrete thereto.
In order to achieve the above object, according to one aspect of the present invention, there is provided a structure of a floor slab bridge comprising a plurality of columnar H-shaped steels each of which includes a web plate having at an upper end thereof an upper flange and at a lower end thereof a lower flange, the columnar H-shaped steels being arranged in side-by-side relation with an end face thereof abutted with a corresponding end face of an adjacent columnar H-shaped steel, the upper flanges being smaller in width than the lower flanges so that a concrete inlet port is formed between adjacent upper flanges; a lower concrete layer formed by placing concrete in a space defined between the upper and lower flanges and between the adjacent web plates through the concrete inlet port; an upper concrete layer formed by placing concrete on the upper flange and connected to the lower concrete layer through the concrete inlet port; a horizontal iron reinforcement horizontally laid on each of the upper flanges; a suspending iron reinforcement suspended in the space through the concrete inlet port; and the horizontal iron reinforcement being embedded in the upper concrete layer and the suspending iron reinforcement being embedded in the lower concrete layer.
By the horizontal iron reinforcement and the suspending iron reinforcement suspended therefrom, the joining strength between the upper concrete layer and the lower concrete layer, particularly the lower concrete layer demarcated by the web plate is properly reinforced, thereby providing sufficient strength to the entire floor slab bridge.
Thus, the shearing resisting force of the concrete against the live load is increased to effectively prevent cracking.
The columnar H-shaped steels generally of JIS specifications each having an upper flange which is cut in such a manner so as to have a predetermined width are arranged in a side-by-side relation between adjacent bridge legs with the adjacent lower flanges abutted with each other, and concrete is placed thereon. Merely by doing so, a floor slab bridge can be constructed at a low cost and with a reduced amount of labor time.
According to another aspect of the present invention, there is provided a structure of a floor slab bridge comprising a plurality of columnar H-shaped steels each of which includes a web plate having at an upper end thereof an upper flange and at a lower end thereof a lower flange, a joining plate made of a steel material being interposed between every adjacent pair of lower flanges, left and right end faces of each of the joining plates being in abutment relation with corresponding end faces of lower flanges of the adjacent left and right columnar H-shaped steels, a concrete inlet port being formed between every adjacent pair of upper flanges with the help of the joining plate; a lower concrete layer formed by placing concrete in a space formed between the upper and lower flanges and between the adjacent web plates through the concrete inlet port; and an upper concrete layer formed by placing concrete on the upper flange and connected to the lower concrete layer through the concrete inlet port.
By employment of the joining plate, the time and labor for dimensioning the upper flange smaller in width than the lower flange can be eliminated. The columnar H-shaped steels of JIS specifications can be used as they are. Accordingly, a floor slab bridge can be constructed at a low cost and with a reduced amount of labor time. Moreover, by properly selecting the width of the joining plate, the width dimension of the bridge can be set easily.
According to a further aspect of the present invention, there is provided a structure of a floor slab bridge comprising a plurality of columnar H-shaped steels each of which includes a web plate having at an upper end thereof an upper flange and at a lower end thereof a lower flange, the columnar H-shaped steels being arranged in a side-by-side relation with an end face thereof abutted with a corresponding end face of the adjacent columnar H-shaped steel, the web plate being pierced therethrough by a web through-bar, a plurality of the web through-bars being arranged in the longitudinal direction of the bridge at small intervals, a stopper such as a nut, which is to be abutted with an outer side surface of each of the leftmost and rightmost columnar H-shaped steels, the upper flanges being smaller in width than the lower flanges so that a concrete inlet port is formed between adjacent upper flanges; a lower concrete layer formed by placing concrete in a space defined between the upper and lower flanges and between the adjacent web plates through the concrete inlet port; an upper concrete layer formed by placing concrete on the upper flange and connected to the lower concrete layer through the concrete inlet port; and the web through bar being embedded in the lower concrete layer so as to serve as a concrete reinforcement, opposite ends of the web through-bar and the stopper being embedded in side concrete layers which are placed on outer side surfaces of the leftmost and rightmost columnar H-shaped steels.
The web through-bar is preferably of the type having a head (stopper) at one end thereof. A nut (stopper) is threadingly engaged with the other end of the web through-bar so as to fasten to the outer side surfaces of the web plate of the leftmost and rightmost columnar H-shaped steels. It is also accepted that a nut is threadingly engaged with each end of the web through-bar to fasten to the outer side surfaces of the leftmost and rightmost columnar H-shaped steels.
This fastening force is preferably not so large so as to give an abutting force to the abutting parts of the adjacent lower flanges of the columnar H-shaped steels. That is, it is preferred that the adjacent lower flanges of the columnar H-shaped steels are merely loosely contacted (a small space may be formed between the adjacent lower flanges) with each other.
The web through-bar is embedded in the lower concrete layer so as to serve as a concrete reinforcement. Moreover, the shearing resisting force against the live load to be imposed on the concrete layer is increased. This effectively prevents concrete cracking. In addition, by embedding the stoppers and opposite end parts of the web through-bar in the side concrete layers, they can be prevented from becoming rotten due to wind, rain or the like and the outer appearance is not spoiled.
Preferably, the joining plate is provided with a reinforcement plate which is erected from an upper surface of the joining plate and embedded in the lower concrete layer. Due to this arrangement, the main girder component members of a bridge can be increased in strength, and the joining plate and the lower concrete layer can be firmly joined together.
The horizontal iron reinforcement and the suspending iron reinforcement may be used in combination with the joining plate and the web through-bar, where appropriate. By doing so, those elements can function synergistically.